First commercial oil flow tested offshore Ireland

An appraisal well in the North Celtic Sea basin has turned in the first commercial oil flow rate offshore Ireland.

The 48/24-10z Barryroe appraisal well stabilized at rates of 3,514 b/d of oil and 2.93 MMscfd of gas with 517 psia wellhead pressure on a 68/64-in. choke without artificial lift. The test rate is nearly double the predrill commercial threshold, said Providence Resources PLC, Dublin.

Oil formation is the Lower Cretaceous basal Wealden sandstone at 7,400 ft. Next steps are to test the upper gas-bearing basal reservoir zone, commingle the two zones, suspend the well for a possible sidetrack, and compare log and well data with 3D seismic.

Providence operates the SEL 1/11 license with 80% interest. Lansdowne Oil & Gas PLC has 20%. The well is in 100 m of water 50 km off southeastern Ireland.

The well flowed from a 24-ft net pay perforated interval. It was tested using vacuum insulated tubing across the upper 2,600 ft of the total test string due to equipment availability constraints. Lab analysis confirms the oil as light, 42° gravity with 20% wax content, in situ viscosity of 0.68 cp, and 800 scf/stb gas-oil ratio.

Tony O’Reilly, Providence CEO, said, “Our comprehensive wireline logging program has revealed the seismic signature of the basal sands and can therefore be used to map these intervals directly in the 3D seismic volume for field volumetric determinations and sidetrack well planning.

“The most recent development planning carried out by RPS Energy cites the use of high angle oil production wells which should provide significant incremental production potential over this simple vertical well.”

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Providence expected a slightly higher wax content than the 1990 offset well and did not expect as low a viscosity as 0.68 cp, which is lower than water, O’Reilly added, indicating suitability for future waterflood (OGJ Online, Oct. 19, 2011).

The current development concept involves the use of horizontal wells with artificial lift such as electric submersible pumps. The 3D has also confirmed that fault density in the basal Barryroe sands is relatively low versus the overlying Seven Heads field. Also, the planned horizontal wells provide a further mitigation against any potential compartmentalization.

At Barryroe, Providence said, the primary basal sandstone reservoir can now be seen in five wells that have been drilled to this depth and this covers a 20-km east-west strike and 300 sq km areal extent, equivalent to a medium to large North Sea oil field.

An audit of Barryroe carried out by RPS Energy for Lansdowne in 2010 indicated P50 and P10 estimates of 373 million bbl and 893 million bbl, respectively. The corresponding 2C and 3C Barryroe technically recoverable contingent resources in place were 59 million bbl and 144 million bbl, respectively.

The resources should be enhanced by the increased sands and deeper oil-water contact. The 3D should allow for the better picking of the oil-bearing reservoirs. And because the RPS report only focused on the shallower Middle Wealden sands, not the basal sands, these sands will need to be factored in, Providence added.

The flow rate from the basal sand package was 146 b/d/ft from a vertical well, but horizontal wells will expose much more reservoir and could support much higher production rates. Providence will engage with suitably qualified farmees with expertise in offshore field development and operation to mitigate the company’s development CAPEX exposure in return for equity/operatorship.